We know we need an (x + _ ) and a (2x + _ ) because 2x times x is 2x^2 Now we just need to know what will give us the 5x in the middle and the 2 at the end
a 2 times a 1 would give us the 2 on the end. So lets make sure that works
(x+2)(2x+1) use the distributive property or foil to check this.
x times 2x = 2x^2
x times 1 = 1x
2 times 2x = 4x
2 times 1 = 2
Combine all the like terms
2x^2+x+4x+2
2x^2+5x+2
Looks like that checks out.